Drafting apparatus



I Sept. 19, 1.944. A, LANGSNER 2,358,522

u DRAFTING APPARATUS Filed May 8, 1939 s sheets-Sheet s l INVENTOR. dagp/vayJ/fzef ATToRNEY f `Patented Sept. 19, 1944 UNITED STATES PATENT oi-Fics l Drmrmsliita'rus I y Adolph Langsner, Chicago, Ill., assignor to Eugene Dietzgen Co., Chicago; Il1.,:a. corporation oi"Y Delaware Application May s, 1939, serial No. 272,335 fao claims. (ollas-49')` My invention relatesin general to parallel motion devices and more especially to draftingv equipment embodying parallel motion mechanisml the invention relating more particularly' to a device adapted for attachment on a drawing board or table in order to element, such as a straight edge, for freek and unrestricted movement on the board or table, while'maintaining the ruling element in an adjusted relative angular relation with respect to the board or table throughout the movement of the guide element Within said drafting area.

An important object of the inventionis to provide parallel motion apparatus in which the ele- ,7. ment supported for parallel movement is carried onA a jointed arm, including flexible, rendless belt means operating on pulleys at the opposite ends of the arms for maintaining the supportedA device in a desired alignment, regardless of the movement of the arm. ,Y l

Another important object resides in providing apparatus of the characterv mentioned, wherein the relatively movable arms are of simplied construction, each comprising tubular connecting means extendingV between pulley housingsand supporting the housings in spaced relationship whereby an inexpensive, lightweight, andadequately rigid arm construction is provided; a further object being to utilize the tubular means for the purpose of iiexible driving element, While at the Sametime holding the pulley housings in spacedrrelationship.

Another important object is to provide yielding means neatly and compactly arranged to normally urge the flexible driving element in one direction on said pulleys; a further object being to utilize a helical spring extending within one of the tubular spacing and enclosing members, with the flexible driving element extending axially .through said helical spring, whereby to conserve space and permit the spring and driving element to be snugly enclosed while freely operable within the tubular element. 'Y Y,

Another important object is to provide means readily operable to adjust the tension appliedon the driving element by the helical spring, it being understood that the spring, in urging the driving member in one direction on the pulleys, tends to rotate the arm about the 4supported end thereof in one direction whereby to counterbalancethe .weight of said arm particularly when the device .is mounted on a support for movement Vin a plane tilted Yfrom the horizontal; va further'` important support a ruling guide within a drafting-area lil housing and protecting the object being to utilize, as tension adjusting means, a manually-operable" tensioning element supported on a pulley housing for adjusting movement thereon, including means for anchoring the manually-operable element in adjusted position on .the housing.

j Another important object is to form the manually-operable element as a crank having a pulley or 'winding drum thereon for winding a tension element connected with the spring for tensioning Y the same. i

Another important object resides in providing a tiltable lever on the housing/and angular-ly adi justable thereon for spring tension. n n ,Y j Among the numerous ,other objects and advantages'of my present invention isthe' provision of neat, compact and attractive parallel motion mechanism wherein'the weight of moving. parts is 'reduced to a minimum, all ofthe parts being entirely lenclosed and housed against mechanical 'damagefrom outside forces and from deterioration through yexposure to thejatmosphere, vthe novel structural features Vof the apparatus, in addition, lending themselves to the provisionof attractive Vstreamlined appearance in the lnished article.'

The foregoingand numerous'V other` objects, advantages and inherent functions ofLmy present inventioniwill become apparent as the same is more fully understood from the following de- 'scriptionuwhich taken in connection with rthe -,accompanying drawings, discloses a preferred jembodimentof the invention. Y,

Referring to the drawings, Y Y j`Figure 1 is atop plan View of4 parallelmotion mechanismembodying my present. invention, partsof the apparatus being'broken away Vto illustrate the internal construction thereof;

Figures Zand 3 ares'ectional viewsgtaken subthe purpose of adjusting Astantially, along Athe linesv2-2 and 3+'3, respectively, in Figures 1 and 2, in order to illustrate an ,improved tensioning means for the driving bands;

,j Figures 4, ,5, 6 and 7, respectively, 'areenlarged j [preferred manually-operable' tensioning Ymeans kfor adjusting ,yielding counterbalanced means .forming a part ofA he device of my'pres'ent'invention; W

Figure 9 arplan view of the yQte'n'sioning device ,shownin FigureS; 4 i ,55

rieures 1o, 12 and 14` are' pianyiws-sicwmg tion about an axis 35 adjacent an end of each I arm, means 31 being provided at the opposite end of the arm 3| for anchoring it on a drafting board or table for relative rotation about a,sta..

tionary axis preferably formed by a stationary pin 39. The end of arm 33, opposite from the pivot 35, carries means 4I element 43 for parallel movement, said element, in the illustrated embodiment, comprising drafting guide means adapted to be moved throughout a drafting area on 'the drawing board or table on which the mechanism is or may be attached. f

The arms 3| and 33 are preferably of substan` tially Videntical construction and may comprise each a pair of housing elements 45 and a pair of hollow, tubular spacers 41, the opposite ends of Vwhich are secured to the housing elements for supporting an V for `free rotational movement on the Within the housing element and having a rim 65 extending adjacent and within the rim 49 of the casing. The pulley 63 has a hub fixed on the pin or shaft 39 so that the pulley is held from rotation with respect to the mounting means 39 and the table on which the device is or may be attached.

TheA open vend-of the housing may be and preferably is venlclosed -by suitable cover means 66 supported on the shaft 39, and while such `cover means may take any suitable or convenient form and may be formed on or carried by the pulley 63, if desired, I prefer to mount the cover pin 39 so that the .casing30 and cover 66 may form a closed leasing around the pulley 63.

In theillustrated embodiment the device or element 43 supported for parallel movement comprisesl a bracket 61 supporting straight edge elements 69 at right-angles, one with respect to the other, although it is, of course, apparent that 45 to support the same in spaced-apart relationship. The housing elements of the arm ,3| vare individually identified by the numerals 3|)V and 32, while the corresponding elements of 'thearm 33 are identied by the numerals 34 and 36.

AThe housing elements 45 preferably are of substantially identical construction for conven- K ient and inexpensive fabrication, and they preferably comprise, generally, shallow casings', each Vhaving a rim 49 and a closed end wall 5I, the

opposite endbeing open. The end wal1'5 I, within the rim 49, carries an annular flange 53 preferably formed integral with the wall 5| and extending inwardly of said Wall in positionY to form a seat for a bearing 55of 'any suitable or preferred construction, and which, asshown on the drawings, may be a roller or ball bearing.

The casings 30 and 32, which are at the'opposite ends of the arm 3|, as well as the casing 36, which is at the free end ofi the arm 33, are Varranged with their'ope ends facing downwardly toward the surface on which the device is mounted. The casing 34 atthe endof the arm 33, which is secured'to the arm 3|, is larranged 'with its open end facing upwardly, opposite the open end of the casing 32, so that the casings 32 and 34 cooperate to form a housing. This housing encloses a pulley 51 having a rim 59 extending in the peripheral portions of the compartment formed by the cooperating Vlcasings, 32 and 34. The pulley' is mounted on a pin 6| and journalld for rotationin the bearings 55 of the casings 32 and 34, the pin 6I serving to hold the casings together by cooperation with said bearings.

It will be noted that the pin 6 I has a nut threaded thereon at one end, and Vthat the endV the invention is not necessarily limited to the specific character of the supported element 43. Means 4| jis provided to mount the supported element 43 upon the easing I6 at the free or swinging end of the arm 33, the means 4| comprising a pulley 1| carried on a pin 13 and journall'ed for rotation on the housing element 36 by means of the bearing 55 in said housing.

It will be noted that the pin 13 is fast with the pulley 1 the pin having a head extending downwardly of and lprojecting from the lower, open end of the housing in position to support the bracket 61 which forms a part of the supported element 43. The bracket 61 is carried by the pin, 13,'and means, including the clamp 15, is provided for adjusting the relative angular relationship of the supported device 43 with respect to the pulley 1| and for locking the parts in a desired adjusted relationship, the angularity of which may be determined on a scale 11 carried by the pulley 1 I. At its end opposite the head, the pin 13 lprojects upwardly of the bearing through a central opening formed in the wall 5| ofthe housing 36, and this end is provided with means for attaching a knob or hand piece 19 to aid in the manipulation of the device. VIn the illustrated embodiment the hand piece 19 is fastened lon the pin 13 against turning movement.

flhe rim 49 'of each of the casings 30, 32, 34 and 36 is or may be formed with a pair of preferably integral projections 8| extending tangentially of the rim 49, 'said projections on each casing being parallel and spaced apart on opposite sides of the casing. The projections 8| are each formed with a preferably accurately defined seat 83 adapted to snugly receive the end of a spacer tube 41. Thebottom of each seat is connected with the interior of the casing on which it is formed, by means of an opening85 so that when the end of a tube 41 is assembled in the seat 83 the interior of the tube is connectedwith thev into the sockets or seats '83, the tubes forming is preferably pivotally mounted upon a shaft or pin 39, said shaft being preferably fixed on and forming a part of the clamp means 31 by which thev device is or may be fastenedupon the Vdrawing board or table. The housingelement'30. is

journalled on the pin 39 by. means of. its bearing 55. The pin 39 also carries a pulley 63 extending adequately rigid connection betweenV the casings and'servng to maintain'thecasings in accurately spaced apart relationship, at the same time providing an extremely lightweight arm structure.

It will' Lbe noted that the 'casings 32 and 34 'cooperate' to form ajsubstantia-lly closed housing or* r the pulley 51; that `the housing 3|), in conl'junction win-the cover ymeans 66, likewise forms nected ends of the arms 3| and 33 is formed 'with a pairA of grooves in its rim. The grooves in allof the pulleys 51, 63 and `1|, however, are of like width and depth, and are adapted to receive flex' ible driving means 81 preferably comprising anv endless belt in each of the arms 3| and 33. These belts may conveniently comprise lengths of metal tape, the opposite ends of each tape being con-Y nected together by fastening means 89 allowing for adjustment so that the flexible driving means may be drawn up to a. desired tensionon the carrying pulleys.

The tape-like elements Vforming the flexible driving means may be appliedon the pulleys in each arm by threading the same endwise'through the open side of the housing element 30, in the case'of arm 3|, and through the open side of the housing element 36, in the case of the arm 33, before the pulleys 63 and 1| are assembled in place. vThe tape is passed through one of the tubes 41 toward and around the pulley 51. The

flexible elements of both arms 3| andr33 may thus be drawn raround the pulley 51 andreturned, one through the remaining tube of the arm 3| and the other through the remaining tube of the arm 33, back to the starting point. It will be noted that the pulley chamber in each casing extendsA into the base portions of the projections 8|, thereby' yproviding openings ac cessible fromthe under side ofthe armassernbly to facilitate .drawing the flexible members through the tubes'41 and around the pulleys in applying the same. In addition, openings 82 may, if desired, be formedV in theztopof the housings for this purpose. After theiiexible driving means have thus been assembled in each of the 'arms 3| Vand 33, the abutting ends of each mayv be connectedA together by the connectors 89. Then the pulleys 63 and 1| .may be assembled in place.

The connectors 89 may be V'of 'any suitable 4or preferred construction, but, as shown in the drawings, the same mayeach comprise a stem 9| have ing a diametral slot 93at one endadapted to receive an end of the ilexibledriving member 81 which is secured in the slot 93 by rivets 95 or other suitable fastening. The stem 9| has a lug 99Y formed with an opening to receive one end of a spring |I, the opposite en d of which is connected on a lug 98fformed in the end ofva threaded stem 96 formed with a diametral slot 94 to receive an adjustable connector piece |02. Thisfpiece is of plate-like form adapted to slidingly't the slot 94 and it has a necked portion |03 of width not greater than the diameter` of theV stem 96 so that a nut Y| 05 on the stem 96 may encircle the necked portion |03. The connecting piece |02 has a head |01 extending outwardly of the slot 96 on opposite sides ofthe stem in position to bear upon one end of the nut |05. Consequently; after the driving bands"81 have been assembled injthe armsV 3|'and 33, as heretofore described, the abutting ends of the -bands may be connected together simply by attaching one Yof said ends inthe slot 93 andattaching the othergend'on the connector'piece |02. vThis done, it Yis merely necessary` to thread-the until a desired tension is' obtainedv in the driving element, and thenut |05 may have radial sockets therein adapted to receive a tool to facil-k itateV the tightening of the nut on the stem.

Tightening of the nut may be readily accomplished through thev opening at the base of the projections 8|; I

It will be seen that as thenut is tightened, the spring |0| Will be Vplaced in tension .to anydesired degree within limits determined by the length-of the stem 96 and the position ofthe nut |05 thereon. The spring |0| will substan-y tially maintainrthe band 81 under resilient ten-V sion at all times and will automatically com-l pensate for any slight stretching of `the band 81 that may occur while the device is inservice.V

The flexible driving belts 81 are tightened sufficiently to provide appreciable frictional grip upon the pulleys. Since the pulley-63 is held against rotation With respect to the drawing board or table, it will hold'the exible connector 81 of the arm 3| because of the frictional driving engagement between said pulley 63 andthe flexible connector. As the arm 3| is swung about the pivot pin 39, however, the driving connection between the flexible connector of the 'arm 3| and the pulley 51 will cause said pulley4 to rotate in the casing 32 through an angular displacement equal at all times `to the angular movement-of the arm 3l about Vthe pivot pin 39. In like fashion, the ilexible connector-81 of the arm 33, through its frictional driving engagement on the pulley 51 and on the pulley 1|, insures that the angular moveof the housing 34 with respect to thepulley 51,A

ment of the pulley 1| with respect to the housing 36 is at all times equal to the angular movement thereby insuring thatthe supported element 43 is at all times maintainedk in anadjusted,r angular I' 40 relationship with respect to the board or tableson which the device is mounted, regardless of .the movement of the arms 3| and 33. The desired angular relationship, ofcourse, may be adjusted by manipulating the means 4|, including the clamp 15, as is well understood in parallel motion mechanism. 1

The device of my present invention is adapted for use on drawing boards and tables which may be inclined or tilted more orfless from horizontal position. When used on atilting board, a device of the character described will have a tendency to slide, under the influenceA of gravity, down-l wardly on the board, the `arm 3|, as shown in Figure 1, tending to rotate in counterclockwise 7 direction about the anchored pivot 39, and the arm 33 tending to rotate in `clockwise direction, as shown in Figure 1, about the pivot 6|. In order to counterbalance this tendency to slide, I provide resilient counterbalancing means .cooperatively connected between one or both of the belts 81 and the frame on which mounted. The counterbalancing means is arranged to apply a yielding and adjustable bias upon the frames 3| or33 or both, whereby to resist the turning movement of the arms, under the influence of gravity, on a tilted support. Y Y n To this end,rI prefer to provide a resilient spring lrconnected at one end on the belt81, as by means of a hook |3 carried by the tighten'- ing device 89, the hook ||3 being .preferably secured in the slot 93 of the stem 9|. The other end of the spring is adjustably securedV on the tilting frame, preferablyat one of the housingsl 45Vat an end of theframe, and Iprovide manually operable adjustingmeans for varying nut |05Son` the stem 96 and draw the same down 4 the tension of the counterbalancing means whereby readily to condition the device to counterbalanoe the slipping tendency of the arms when mounted on a tilted support.

An important feature of my present invention is the arrangement of the resilient tensioning means neatly and compactly Within the tubular members l41. To this end, the resilient tensioning means may comprise helical springs IH, one for each of the arms 3| and 33. This helical spring preferably has an internal diameter appreciably greater than the largest cross-sectional dimension of the flexible driving element 81 so that said spring may be assembled in position encircling a portion of the driving element, without, however, binding upon the element or interferng in its operation. The spring also is of a .size to fit freely Within one of the spacing tubes 41 without binding, 1

The counterbalanoing spring means |v| may be arranged in either of the arms 41 of said frame, providing, however, that the spring is arranged to exert tension on the band 81 in a direction to urge rotation of the arm opposite to that in which it tends to turn under the influence of gravity on a tilted support.

The spring may be'arranged in the -upper arm 41, as indicated in Fig. l of the drawings, and, as shown more particularly in Figures 8-15,

Vthe spring may be connected with adjusting means on the pulley housing 45'at the swinging end of the arm 3|. The springrneans however, may equally well be arranged vin the lower arm 41 of the frame 3| and attached on the housing 45 at the pivoted end of the frame 3|. likewise, if desired, counterbalancing "spring means may be applied in the arm y33, although the necessity for counterbalancing'the swinging arm 33 is not as great as the need for balancing thev arm 3|, and consequently counterbalanoing means will ordinarily be omitted from the arm 33.

As shown in Figures 8, 9, 10 and 1l, the adjusting means may comprise a. fitting formingV a pulley or drum |2| movably mounted on the frame 45 and adapted to receive a flexible connecting member |23, one end of which is attached to the spring as by forming a knot in the vend-of the member |23 and clamping the v,knot between the coils of thespring y Asshown in Figures 8 and 9, the -|2| is formed with a slot |25 adapted :to receiveA the knotted end of the vmem-ber |23, and the .drum .|2| is formed with a stem |21'journalled in the housing 45 and having an end extending outwardly thereof. Said outwardly extending end passes through a washer |29 and carriesv a exible spring arm |3| extending .therefrom and carrying a knob |33, whereby the-drum |2| may be turned. l i

Outwardly of the arm |3| the projecting 'end of the stem |21 preferably rcarriesarigidv plate |35 extending outwardly and oppositethe resilient member |3| to form a guard therefor.

The knob |33 `provides a latching projection |31 on the side of the arm` |3| facing vthe wall of the housing v45 which is provided withy a plurality of openings |39 preferably on opposite -sides of the stem |21. The .openings |39 -form flatch keepers for receiving the projection |31, theresili ient arm .|3| normally `urging the projections into keeper-.engaging position in 'the openings `|39.

'By drawing the knob |33 outwardlyiof the hous- 'ing 45 and into engagement with the guard A35', the projection 31 may be released from the keep,-

gesetze er,gwhereupon the winding drum |2| may be turned ,in order towind the member |23 thereon and thus tensiony the spring ||l to a desired extent., The device may be latched in any of the j openings |39 to maintain the spring at a desired tension. Y

As shown in Figures 10, 11, 12, 13, 14 and 15, the tension adjusting means may comprise an arm or frame tiltably mounted on the housing 45 for movement to a plurality of adjustable spring tensioning positions |51. This is accomplished in each case by providing an arm |43 tiltably mount-` ed on the housing 45 and having manually operable means |59 on the arm for moving and latching the same on the housing 45 in a selected one of theV plurality of latched adjusting positions |51; and means is yprovided for attaching the spring on the member |43 whereby to tension theV spring in accordance with the movement of said arm.

The arm.|43, in Figures 10, 1l, 14 and 15, is mounted for tiltable movement about the axis oi the pulley enclosed in the housing 45.

As shown in Figures 10 and 11, the pulley |2| is rotatably mounted on a frame stem |4| forming a part of a frame |43 which'is journalled on the outer walls of the annular portion 53 of the casing 45, being held in place by means of an annular retaining plate 54 which may also serve to hold the bearing 55 in place on the housing 45. The pulley |2| is thus supported for movement Vwith the frame along a curved path |45, the center of curvature of which is the axis of thebearing 55,.

The pulley |2,| is held on the stem |4I by means of a pin |41 having a headed end |49 and a threaded end |5|. The pin |41 is mounted in a channel formed through the stem |4| and is assembled therein with the threaded endv extending below Vthe pulley |2| which is retained in place VVon the stem |4|` by Vmeans of a holding nut |53 or other suitable holding means.

The headed end of the stem projects outwardlly through a, curved slot |55 formed in the housing 45, said slot extending opposite and coinciding with the curved path of movement of the pulley, Vsaid slot |55 being enlarged at intervals, as at |51, to form latch keepers for receiving a latch formed as a knob |59 slidable on the headed 'end of the stem |41 and normally urged by means of a spring |6| on said stem in a direction to latchingly engageV the latch knob |59 in the keeper'openings |51.

VThe tension element |23 passes around a guide pin |66 and thence around the pulley |2 and is anchored at its end on the frame 45 as by passing said end through a perforation |63 formed in a Wall of the housing 45 and knotting the end of the member |23 outwardly of said casing, the knot being received and concealed in -a countersunk opening |65 forming a knot-receiving seat.

In the embodiment illustrated in Figures 10 and 1l, the slot |55 provides ve latching positions |51, the tension of the spring being adjusted by lifting the latching knobV |59 and turning the frame |43 until the desired tensioned position is reached by the knob, whereupon the knob may be latched in .the selected keeper opening |51,

As shown in Figures 12 and 13, the arm |43 ycornprisesa `sheet metal plate pivotally securedV on the housing 45, as by means ofthe screw |61, to `swing in an arc opposite the housing portion 8| atthe vend ofthe spring The arm |43 is of resilient character and carries the knob 59 thereon, which knob has a latching projection at :2,35'8g522 |69 inposition to 'engage any one-onza plurality of openings |51 formed in the casing portion 8|.

'Ihe arm |43 also is provided with'aslot |1|1in position to sweep over a slot |13 formed inthe housing portion 8| 'I'he end of the spring is built to extend upwardly through the slots 1| and |13 and is curled, as at |15; to retain the same in the slots whereby they arm HIS-,is directly connected 'on the spring which may betensioned in accordance withV the adjusted 'and latched position of the arm |43 on the frame; I

As shown in Figures 14 and 15, the'frame '|43 may be pivotally mounted on the pin or stemon which the casing 45 is supported. The arm |43 may extend in position overlying the closed end of' the housing 45 and around the peripheral margin thereof in which the latching-.openings |51 may be formed. VThe overhanging end of the arm |43 is preferably provided with'a latchpin |11 having a head or knob |18 ancla latching end |8| in position to engage the detent openings |51. 1 '1 Y Spring means |19 is provided on 'the arm'l y| 43 Yin'gpulleys.spaced apart thereon, meansrto' support onev of said Apulleys whereby the arm is swingable about the axis of said pulley, drafting g'uide support means carried by they other pulley,

flexible driving means on said pulleys, and helical spring means encircling said driving means fand' normally urging said driving means in one direction' on said pulleys.

4. Ina parallel motion apparatus of the char-V acter mentioned, means comprising an arm having pulleys spaced'aparlt thereon, means to support one of' said pulleys' whereby'the arm is in position to normally urge the stem |11 in a direction'to engage the detent'en'd |8| thereof in said openings. The arm mayA bei released .for adjustable movement by drawing the knob |18 outwardly, and said arm contains achannel and a knob seat |83 on which the end of the flexible tensioning member |23.may'be attached.

The device of my present invention has several .advantages,including simplicity of construction of the arms 3| and 33, lightness in weigh'tfof moving parts; the provision of simple, easily operated means for tensioning theA flexible-'driving belts 81 and the housing thereof VYwithin the spacing tubes 41, thereby effectively enclosing the same and improving the appearance of the apparatus; the provision of` counterbalancing springs and the neat, compact arrangement thereof around the flexible driving belts within the spacing tubes 21;r and also the' simplified arrangements for adjusting the tension YofY the counterbalanoing springs. 'v

It is thought that the invention and numerous Q5 of its attendant advantages will be understood from therforegoing descriptionpandit is obvious that numerous changes may be made rin the form, construction and arrangement of the several parts without .departing from the spiritfor scope of the invention, or sacrificing any of its attendantadvantages, the form herein described being a'preferred embodiment for the purpose of illustrating'the invention. Y

The invention is hereby claimed Yas -follows: 1 .-1. In a parallel motiondrafting device, in'A combination, an arm, a pulley at each encl thereof, means permitting relative movement between the arm and the pulleys, respectively, an endless belt about the pulleys, and tension meansr extending from the belt to the arm. -Y Y l 2. In a parallel motion apparatus of the 'character mentioned, means comprising an arm having pulleys spaced apart thereon", flexible driving means on said pulleys, a spring'connected'on said flexible means and adjustably anchored on said arm under tension to' urge said flexible `means in one direction on said pl'illeyspmanually'operable means to adjust the lanchorageV of said spring, comprising a member shiftable on? said swingable about the axis of said pulley, drafting guide'support means carried by thev other pulley, flexible driving means' on said pulley's,'and helical spring means'encircling said driving means and normally 'urging' said driving means in one Vdirection'on'saidpulleys, comprising spring means connected 'on' -said'driving means and anchored under tension, whereby the'spring'may'resiliently` urge the driving means in one direction.' `5. In a parallel motion apparatus of the '"cliaracter mentioned, means comprising an arm having pulleys spaced apart thereon, means to support one of said pulleys whereby the "arm' is swingable about the axis of said pulleyjdrafting guide'support meanscarried by the other pulley, flexible driving means on Vsaid pulleys, and means normally urging said driving means in one direction on said pulleys, comprising springmeans connected on said driving means and'anchored under tension, whereby the spring may Yresiliently urge the driving means in one direction, and means comprising a shiftable member 'ion Vsaid arm and connected with said spring `means'ffor adjustingthe tension ofv said spring means.

6. In a parallel motion apparatus of the character mentioned, means comprising an arm having pulleys Vspaced apartthereon, means to support oneof said pulleys whereby the'arm is swingable about the axis of said pulley, drafting guidesup'port means carried by the other pulley, flexible driving means on saidpulleys, a spring connected on said flexible means and adjustably anchored on said varm under'tension to' urge said flexible means in one direction -on' said pulleys, and manually Operable means comprising a shiftable member on said arm and connected with saidsprin'g means 4to adjust the anchorage of said spring whereby to'var'y the spring tension exerted on said flexible means.

7.'In' apparatus of the character described, a pair of frames each comprising a pair of spacedapart housing portions members therebetween, means forming a pivotal connectionbetween saidv frames with one of the housing portions of one frame co-operating with one of :the housing portions of' the other frame to form a pulley enclosure at .said connection, a common pulley in said enclosure, said common pulley being angularly movable 'with respect-to .both-frames about the axis of said pivotal con-V fandv tubular spacing between "and Within the'tubular members thereof, and driv'- lingly connecting the cominon'and Ythe swinging pulleys Within the housings at the'oppo'site ends of said other frame", and means supported on said swinging pulleyF` for parallel movement. therewith. "Y l Y ..V

8. In apparatus' Voffthe character described comprising a frame carrying, in spaced'relationship thereon, a pair of transmission rmembers forming supports angularly movable with respect to the frame; and flexible driving means rinclud-- ing an elongated tension member on and extending' between said supports and drivingly interconnecting the same, said frame providing f a tubular duct between said supports for housing portionsofsaidtension member between Asaid supports, the combination; with said tension Vmember and frame, of a helicalspring encircling a portion of said 'tension member within saidductsand'interconnected between said tension memberandsaid Vframe t'o normally Vurge the`driving means in'onei direction on said supports. M H

9; In la parallel `motion apparatus of the charactermentionedthe combination with means comprisingan arm having pulleysV spaced apart thereon, flexible driving means on said pulleys, and a spring connectedwith saidilexible lmeans andW anchored on said 'arm to urgeV saidflexible means-in' one-direction onY saidpulleys, of means to adjustthe anchorage of said spring on the arm, comprising a membershiftable on said arm and connected with said spring and Ymeans --to secure-said' shiftable memberinV Aadjusted posi- -tion onsaid arm comprising manually ,operable detent-latch means* operatively'connected between said arm and said'shiftable member.

10. -Infa parallelmotion apparatus of the characterf mentioned, the` combination withmeans comprisingan 'arm' having pulleys V'spaced apart thereon, Vflexible drivingl means Aon said pulleys, and a spring-connectedwith saidflexiblemeans Vandanchored onsaid arm -tonurge` said exible means Ain' one direction on said` pulleys, ofmeans to adjust* the'anchorage of said spring onfthe arm;V comprising zar-member shiftableon `said arnr -andconnectedwith said spring andv'means tov secure said shiftable member in adjustedpositionon'said arm comprisinglatch means, movable on the shiitable member and keeper means formed on said arm, said Alatchemeans being manually operable to release- 'said -shiitable member for movementonfthe arm and to lock the same with said keeper means. Y v 11; In a parallel motion apparatus of the character mentioned, the combination with means comprising'an arm having pulleysispaeed apart thereon, .flexible driving-means on saidA pulleys, and V-a spring connected with said flexible means and anchoredon said arm to urge said exible means in-one directionY on said pulleys, `of means to'adjust'the'anchorage of said'spring on the arm, comprising a member shiftable on said arm and-connected with said spring and means to secure said Ashiftablexmember inf adjusted position` on said arm comprisingv a member pivoted on said Yarm and carrying springpressed latch meansadapted -to lock in keepers formed inV said 12.*In a parallel motion apparatus of the charactermentioned, the combination withV means comprising'an 'arm having pulleys spaced apart thereon,'flexible drivingm'eans on said pulleys, andal s'pringfconnected 'withsaid Yflexible means Aand anchored on said: arm to Yurge 'said' exble means inonedirection Von said pulleys, of means .to 'adjusti theanchorage of said spring on the farm, comprising a member shiftable on said arm "andf'cnnected with said spring and means to S5 'secure said shiftable memberv in adjusted posi- Ation on'said arm comprising manually turnable vmeans on said arm for shifting said member, 'and manuallyvv operable latch means on said turnable means for securing the same in adjusted l Wposition on said arm. u

13'. In `a parallel motion apparatus of the character mentioned, means comprising an arm having pulleys spaced apart thereon, means'to'support one of said pulkeys whereby the arm is i swingable about the axis of said pulley, drafting guide support means carried by the other pulley, flexible Ydrivingl means on saidpulleys, a spring connected on said flexible means and adjustably anchored on saidV arm under tension to urge said flexible` means in one direction on said pulleys, and manually operable means to adjust the anchorage of said spring, whereby to vary the spring tension exerted on said flexible means, comprising a` winding 'drum on said arm, a manually operable crank forturning said drum, a

vflexibleV winding member on said drum and connected with said spring, detent means'formed "on said crank and keeper means formed on said drin in position to receive said detent meansY in any one of a number Vof adjusted positions of said 4crank for latching the crank against rotationof the drum under the influence of said 'springll V14. A drafting machine comprising a 'xed head,a`work head,`lin'k mechanism connecting the xedhead and thek work head, each link of said.- linkA V*mechanism comprising pulleys in spaced relation, a exible band passing around the pulleys and ai member rotatable around a 40 pulley ofa link and means to counter-balance the weight Vofthe links comprising a spring Xed at onefend to said member rotatable around a pulley and connected'to counter-balance the weight of the links. y 45 :175. In a parallel motion apparatus of the'character mentionedythe combination with means -comprising'an arm member, pulleys spaced apart thereom'flexible driving means on said pulleys, a spring connected to-said flexible means and anchored on said arm member, whereby to urge said flexible means in one direction on said pulleys, of meansto adjust the anchorageof said Vspring on said arm member, comprising an adjustable member shiftable on said 'arm member and connected with said spring, and latch means to secure said adjustable member in adjusted ,position on said arm member, said latch means comprising keeper'means on one of said membersand a releasable latch element onV the other member. Y

16. In a parallel motion apparatus oi the character mentioned, the combination with means lcomprising an armv having pulleys spaced apart fthereonfexible driving means on said pulleys,

`and a spring connected with said nexible means and anchored onfsaidY arm to urge said flexible means in 'one direction on said pulleys, of means toadj-ustrv the anchorage of said spring on the arm, wherebyY to alter the spring tension exerted on said exible means, comprising a shiftable member-rotatable onY saidarm about the axis of `one oisaid pulleys and connected with said spring, and means to secure said member in angularly. adjusted', position with respect to the axis 'I5 oi said pulley,- -comprising manually operable 4to adjust the anchorage of said means comprises a detent movably'mounted on said shiftable member, and keeper means formed on said arm in position to receive said detent in any one of la number of angularly adjusted positions of said shiftable member.

18. In a parallel motion apparatus of thecharacter mentioned, the combination with means comprising an armV having pulleys spaced apart thereon, flexible driving means on said pulleys, and a spring connected with said flexible means and anchored on said arm to urge said -exible means in one direction on said pulleys, of means to adjust the anchorage of said spring on the arm, Vwhereby to alter the spring tension exerted on said flexible meansgcomprising a lever pivoted on said arm and having a swingable portion connected with said spring to adjust the same longitudinally, and manually operable latch means co-operatively connected between the arm and said lever to anchor the same in adjusted position on the arm.

19. In a parallel motion apparatus as set forth in claim 18, wherein said manually operable latch means comprises a detent on said lever, and

vkeeper means formed on said arm in position to receive said detentl in any one of a number of adjusted positionshof said lever. A

20. Ina parallel motion apparatus of the character mentioned, means comprising an arm having pulleys spaced apart thereon, means to support one of said pulleysV whereby the arm-is swingable about the axis of said pulley, drafting guide support -means carried by the other pulley, ilexible driving means on said pulleys, a spring connected on said flexible meansfand adjustably anchored on said arm under ltension to urge said flexible means in one direction'on said pulleys, and manually operable means to adjust the anchorage of said spring, whereby to lvary thereon, vflexible'driving means on said pulleys, and aspring connected'with said flexible means and'anchored on said arm to urge saidflexible meansy inone'direction onsaid pulleys, of Vmeans toadjust the anchorage of said spring on the arm, whereby to alter the spring tension exerted 4on Ysaid e'xible means, comprising a lever pivoted4 on saidarm Yand having a swingable portiorr connected with said spring to adjust the same longtiudinally, said arm having a slot extending longitudinally of the spring and said swingable portion overlying said slot, said spring having a portion extending through said slotandV f connected to said swingable portion, and manually Voperable-latch means co-operatively connected between the arm and 'said lever to anchor the same in vadjusted position on the arm.

23. In' apparatus of the character described comprisinga frame carrying, in spaced relationthespring tension exerted on said exible means,

comprising a winding 'drum onsaidarm, amanually operablecrank `for turning said drum; a ilexible winding member on said drum and connected with said spring, detent means formed on said crank, said crank comprising" a blade of resilient material, and keeper means on said arm in position to receive said detent means for latchinsr the crank on the arm.`

r v 21. Ina parallel motion apparatus offthe character` mentioned, theY combination with means comprising an arm having-pulleys spaced apart T thereon, flexible driving meansV cn said pulleys, anda spring connected with said flexiblemeans and anchored on` said arm to urgeV said flexible means in one direction on said pulleys, of`means arm, whereby to alter the spring tension exerted on said flexible means, comprising a shiftable member rotatable on said arm about the axis of one of said pulleys and connected with said spring, and means to secure said memebr in angularly adjusted position with respect to the axis of said pulley, comprising manually operable spring urged latch means on said shiftable member, said arm having a. series of detent openings spaced apart on the arc of a circle centering dn said axis in position to latchingly receive the latch means.

22. In a parallel motion apparatus of the character mentioned, the combination with means comprising an arm having pulleys spaced apart spring on the ship thereon, a pair of transmission members forming supports angularly movable with respect to the frame, exible driving means comprising an elongated tension member on and extending between said SlllJpOrts and drivingly interconnecting the same, said frame providing a tubular duct between said supports for housing portions of said tension member between said supports, vand means interconnecting the opposed Aends of said-tension member to form a continuous band encircling said supports, the combination, vwith said tension member and Vframe, of a helical spring encirclingaportion of said band and ,connected thereto at one end of the spring, the other endof the spring being attached on fsaid frame at one end of said duct.

24. In apparatus of the character describeda frame carrying, in spaced relationship thereon, a pair of transmission members forming supports angularly movable with respect to the frame, iiexibledriving means comprisingk an elongated tension member on and extending between said supports and drivinglyinterconnecting the same, said lframe providing a substantially tubular duct between said supports for housing portions of said tension member between said supports, said vtension member comprising a band havingk abutting end portions,v and adjustable means to adjust the tension in said tension member, said adjustable means forming a spring mount, and a helical spring lencircling afportion of said band within said duct and connected at one end on said spring mount whereby to vnormally urge the Vdriving means in one direction with respect to said supports. 'l f l 25. In apparatus of lthe character described including a frame carrying,` inf spaced relationship thereon, aY pairk of transmission members forming supports angularly movable with respect to the'pframe,A and flexilbe driving means comprising an elongated tension member on and extending between said supports and drivingly interconnecting the same, said frame providing a tubular duct between said supports for housing portions ofMsaid tension member .between said supports, the combination ofy means for adjusting the tension in said tension member between vto adjust the tension in said tension 8 comprising a frame carrying, in spaced relationship'thereon, a pair-ofA transmission members forming supports angularly'movable with respect to the frame, flexible driving means including an elongated tension member on and extending between said supports and drivingly interconnecting the same, saidY frame providing a tubular duct between said supports for housing portions of said' tension member between said supports, and. means interconnecting said tension member to form a continuous band `encircling said supports, the combination, withV said tension member and frame,- of a helical spring encircling a portion of said band and connected thereto at one end of the spring, other end of Vthe spring being attached on said frame at one end of said duct, said interconnecting means comprising a stem attachedV on oneend of said. tension member and having a threaded portion provided with a diametral slot, means on the opposite end of said tension member including a necked portion adapted to extend in said diametral slot, and a-nut on said necked portion and adapted for threaded enga-gement on the'threaded portion of said stem.

27. Inapparatus of the character described, a frame carrying, in spaced relationship thereon, a pair of transmission members forming supports the said. pulleys and housings within said tubular the opposed ends of angularly movable with respect to the frame,

flexible driving means comprisingkan elongated tension member on and extending between said supports and drivingly interconnecting the same, said frame providing a tubular duct'between said supports for housing portions of said tension member between said supports, said tension member comprising a band having labutting end portions, and adjustable means interconnecting said abutting end portions and operable member between the supports, said adjusting means comprising a stem element attached on one end portion of said band and having a threaded portion provided with a diametral slot, means forming a clamp element on the other end portion ofsaid band foradjustably receiving said stem, oneof said elements providing a spring mount, and a helical spring encircling a within said duct and connected at one end on said spring mount and at its other end on said framewhereby to normallyV urge the driving means in one direction with respect to saidsupports--Y Y .1

28. In a parallel motion apparatus of the character mentioned, an arm comprising a pair of housings adapted each to atleast partially enclose a pulley, said-housings being formed on opposite sides thereof, each with a pair of parallel, spaced-apart sockets in position extending tangentially with respect to the pulley in said housing, a pair of tubular spacing members, each tted at one end in a socket of one housing and at the other end in a socket of the other housportion of said bandY members, saidexi'ble driving means comprising Va strip having interconnected ends to 'form a continuousband, and means at said interconnected ends for adjusting the length of said band whereby to adjust the tightness thereof on said pulleys, comprising a stem attached on one end of said strip and having a threaded portion provided with a diametral slot, means on the opposite end of said strip including a necked portion adapted to extend in said diametral slot, and a nut on saidl necked portion and adapted for threaded engagement on the threaded portion ofsaid stem. Y

29. In apparatus of `the character described, a frame, a pair of transmission members angularly movable on the frame, means drivingly interconnecting said transmission members comprising, a band having abutting end portions extending therebetween, adjustable means interconnecting said abutting end portions for adjusting the tension of said tension member between said transmission members, said adjustable means comprising a stem element attached on one of the end portions of said band and havingv a threaded portion provided with a diametral slot, a mounting element on the other end portion of said band comprising a necked portion formed to extend in said diametral slot, a nut on said necked portion adapted for threaded engagement on the threaded portion of said stem, means forming a hook on one of Said'elements, and a helical spring encircling a portion of said band and connected at one end on said hook and at the other on said frame in Vposition to'normally urge said tension member in one direction on said transmission members.

30. In a parallel motion apparatus of the character mentioned, an arm comprising a pair-of housings adapted each to at least partially `emcloseV a pulley, said housings being formed on opposite sides thereof, each with a pair of parallel, spaced apart sockets in position extending tangentially with respect to the pulley in said housing, a pair of tubular spacing members, each tted at one end in a socket of one housing and at -the other end in a socket of the other housing, whereby said tubular members maintain the spaced apart relationship of the housings, and flexible driving means extending on and between said pulleys and housings within said tubular members, said flexible driving means comprising a continuous band on said pulleys, and a helical spring encircling a portion of said band within one of said tubular members and'interconnected between said band and said arm to normally urge ilshe driving means in one direction on said puleys.

Y ADOLPH LANGSNER. 

